image – Made by Mikal

Further adventures with base images in OpenStack

Post author:mikal
Post published:January 4, 2012
Post category:OpenStack

I was bored over the New Years weekend, so I figured I'd have a go at implementing image cache management as discussed previously. I actually have an implementation of about 75% of that blueprint now, but its not ready for prime time yet. The point of this post is more to document some stuff I learnt about VM startup along the way so I don't forget it later. So, you want to start a VM on a compute node. Once the scheduler has selected a node to run the VM on, the next step is the compute instance on that machine starting the VM up. First the specified disk image is fetched from your image service (in my case glance), and placed in a temporary location on disk. If the image is already a raw image, it is then renamed to the correct name in the instances/_base directory. If it isn't a raw image then it is converted to raw format, and that converted file is put in the right place. Optionally, the image can be extended to a specified size as part of this process. Then, depending on if you have copy on write (COW) images turned on or…

Openstack compute node cleanup

Post author:mikal
Post published:December 20, 2011
Post category:OpenStack

I've never used openstack before, which I imagine is similar to many other people out there. Its actually pretty cool, although I encountered a problem the other day that I think is worthy of some more documentation. Openstack runs virtual machines for users, in much the same manner as Amazon's EC2 system. These instances are started with a base image, and then copy on write is used to write differences for the instance as it changes stuff. This makes sense in a world where a given machine might be running more than one copy of the instance. However, I encountered a compute node which was running low on disk. This is because there is currently nothing which cleans up these base images, so even if none of the instances on a machine require that image, and even if the machine is experiencing disk stress, the images still hang around. There are a few blog posts out there about this, but nothing really definitive that I could find. I've filed a bug asking for the Ubuntu package to include some sort of cleanup script, and interestingly that led me to learn that there are plans for a pretty comprehensive image management…

Color ebook!

Post author:mikal
Post published:June 30, 2006
Post category:Imagemagick

By far the most consistent criticism of The Definitive Guide to ImageMagick has been that the sample images need to be in color. I would have to agree with this point, which is why I am delighted that Apress took the time to go back around the production process and produce a version of the ebook with color images. It's cool that they were willing to put in the effort, and not only that, they're giving anyone who has purchased the ebook to date a free upgrade. Even better, now if you buy the printed book on Amazon, you get the color ebook for free! I have a limited number of color ebooks to give away, so if you're interested please leave a comment and explain why you'd like one.

Ruby sample source code

Post author:mikal
Post published:January 13, 2006
Post category:Imagemagick

This is the source code for the imwizard application demonstrated in Chapter 10 of ImageMagick, the Definitive Guide. This is a small Ruby script which demonstrates how to build an interactive program which builds a list of commands to apply to images, and then applies those commands to many images as specified by a regular expression. Extracted source Tarball Zip file

JVC utilities for changing the images and movies on my head unit

Post author:mikal
Post published:November 23, 2005
Post category:Link

So I don't lose them: changing images on your JVC head unit and the JVC windows application which makes it easy.

ImageMagick book – Chapter 2: Basic Image Manipulation

Post author:mikal
Post published:August 12, 2005
Post category:Imagemagick

I'm meant to be writing the rest of chapter seven tonight, but I thought I would warm up by continuing with my promised series of posts about the content of the book. The next chapter in the list is chapter two, which covers simple image manipulations. The idea was to get the stuff which everyone wants to do and cover it as soon as possible so that people can get some runs on the board (so to speak). In chapter two you will find an introduction to the bits of imaging theory that we need for the book (rasters, vectors, bitmaps, pixels, you get the idea). Then I move on to talk about ways to change the size of images. This includes resizing, sampling cropping, scaling, thumb-nailing and so forth. We also discuss some interesting transformations like trim. Then we move onto making an image larger, before finishing up with how to process many images at once with ImageMagick. It's an interesting chapter in that it's immediately useful, and goes through some interesting theory matters. It also sets the stage for the later coverage of all the other cool stuff you can do with ImageMagick. As a point of interest,…